Semiconductor integrated circuit devices

A semiconductor integrated circuit device, comprising:

• a substrate that includes a base substrate of a first conductivity type and an epitaxial layer of a second conductivity type formed on the base substrate;
• a first buried impurity layer of the second conductivity type formed in at least a portion of an interface between the base substrate and the epitaxial layer;
• a deep well of the first conductivity type formed on the first buried impurity layer;
• and
• a semiconductor device formed on the deep well;
• wherein the semiconductor device operates using a first voltage, and
• wherein the first buried impurity layer is coupled to a second voltage greater than the first voltage.